Answer: Nature of the reactants, particle size (surface area), concentration, temperature and catalyst; temperature is explained below.
The rate of a chemical reaction depends on: the nature of the reacting substances, the size of the particles, the concentration of the reactants, the temperature, and the presence of a catalyst.
Temperature: at a higher temperature the molecules have more kinetic energy, so they collide more often and with greater energy. A larger fraction of the collisions has enough energy to break the bonds of the reactants, so the reaction becomes faster. That is why food cooks faster on a high flame and why we keep milk in a refrigerator to slow down souring.